In the conventional type of digital copying machine, a document is scanned and read, and the read image data is stored in a storage means, and a storage start position for the read data in this storage means is regarded as a fixed position corresponding to an upper stream side for reading and scanning. Also Japanese Patent Laid-Open Publication No.268434/1993 discloses a duplex copying apparatus in which a storage device for storing either one of the right and left pages in a spread document is provided and a an image of a page in the next or previous spread page stored in the storage device and an image of a page related as a top or a rear page to the stored page image are copied on both top and rear surfaces of a sheet of recording paper simultaneously. In this duplex copying apparatus, an image storage area in storage device changes, but a position of a document is fixed, and to store images of document having different sizes at a standard position for each size of document, setting a spread document at an accurate page position is required. For this reason, it is essentially required to provide an input means for inputting a document size and decide an image storage range in a storage device according to a document size or to decide an image storage range in a storage device according to a document size by automatically determining a position of the document.
There is no book page image document reading apparatus based on the conventional technology which can read an image of a book page, a corner or an edge section of which is not aligned to the respective reference position when placed on a document base and changes a size of the image thereof. There is a copying machine which can automatically detect a size of a document and select a form for copying the document thereon.
In a book page document image reading apparatus for reading an image of a book page, in a case where a document of spread book pages is placed on a document base aligning the central binding position to the reference point and an image of a spread of book pages is read from an edge section of one of the pages and then the read image data is stored in an image memory, a range of an image data storage range in an image memory when an image is read with a multiplied size is limited due to a limited capacity of the image memory, and sometimes, a portion of an image to be read is lacked because image data for edge sections of an image to be read is lost in the read image data. When a portion of an image to be read is lacked, sometimes the output data is rather unpleasant to see when the image data is outputted from the image memory to a printer or the like and the image is formed.
As a document size is automatically detected in a case of the copying machine as described above, it is conceivable that it is also possible in a case of a book page document image reading apparatus to automatically detect a size of a book page document and decide an image data storage range in an image memory according to the detected book page document size. However in this case, a precision in book page document size detection is low and affected by each book page document, and sometimes it is difficult to detect a size of a book page image because a book page document may include graphics or due to a gap at an edge section of the book page document. Also when automatically and continuously copying a plurality sheets of book page document, different from a case where a sheet document is copied, generally it never occurs that a portion of a book page image is copied, and for this reason it is extremely difficult to detect a size of a book page document. Furthermore, a size of a book page document is generally not a fixed one, so that it is difficult to determine the size.
Also in the book page document image reading apparatus for reading an image of a book page document, if a book page document is placed on a document base with the central binding section being aligned to the reference position, an image of the spread book page document is read from one page edge section, and the read image data is stored in the image memory, an image data storage range in the image memory is limited due to a capacity of the image memory, and sometimes image data for an edge section of the read image is lacked from the read image data.
Namely, in the image memory a position for starting storage of read image is a fixed position corresponding to the upstream side in the reading/scanning direction. However, a position of a page of a spread book page document displaces in association with page turning, so that a position where the read image data is stored in the image memory changes and sometimes the read image data can not be stored within a prespecified image data storage range, and for this reason sometimes a portion of the read image is lacked. In a case where a portion of read image data is lacked, when the image data is outputted to a printer for forming the image on a form, the form may become unpleasant to see.
As a size of a document is automatically detected in the copying machine as described above, it can be considered that a document size may automatically be detected and an image data storage size in the image memory may automatically be decided according to the detected book page document size. However, this case, precision in detection of the book page document size is low and the precision is affected by a type of the book page document in such a case as that where, for instance, the book page document includes graphic pages and a step is generated between edge sections of each page, and in that case it is difficult to detect a size of a book page document accurately. Also in a case where a plurality of pages of a book page document are automatically copied, different from a case where a sheet document is copied, it seldom occurs that only a portion of a page image of the book page document is copied, so that detection of the book page document size is quite difficult. Furthermore, a percentage of book page document having irregular size is substantially high, which also makes it difficult to accurately determine a size of a book page document.